Toyota Repair: 91 Camry hesitates & stalls, damp weather, vacuum hose

Question
I have a 1991 Camry 2.0 4 cyl that started to hesitate or stumble on accelleration (from a stop).  After about a week of this intermittent problem, it stalled at a stoplight.  Started back up right away then stalled again.  Repeated a couple times then wouldn't start.  Towed it home, let it sit and it started.  Changed the fuel filter, spark plugs, distributor cap & wires, air filter and it still hesitates on accelleration.  Brought it to a local shop and they thought it may be dirty injectors, so they did a $79 fuel system cleaning.  Still hesitates.  Toyota dealer checked the fuel pressure, distributor, and coil and they said they were all in specs.  The tech said it seemed minor to him and he wouldn't spend $500 to diagnose the problem.  I don't want to either but it is not a minor problem to me.  The car has around 150,000 miles on it and was running great with no major problems up to this point.  I do get a puff of blue smoke on start-up after it sits a few hours.  It doesn't burn oil otherwise.  Could that be fouling the oxygen sensor?  I've seen a couple other posts that mention stalling and the coil and the EGR valve.  Any opinions?  Also, the low speed on the fan quit working.  Toyotas don't just self destruct @ 150,000 do they?

Answer
It is runs worse in damp weather or rain replace the coil. You may consider the coil anyways. Also something to consider is if you used non factory dist wires, cap and rotor the parts may not be as expected and actually still causing the problem.
The other thing to try is to tap on the egr valve when its running rough. If it starts to run smoothly then unplug the vacuum hose and leave it off  to see what happens. Do plug the line if you leave it off.